Liquid circulation device, adjustment method of the same, and manufacturing method of image formation device

Abstract

To provide a liquid circulation device which properly adjusts a circulation amount of a liquid, and to provide an adjustment method of the liquid circulation device and a manufacturing method of an image formation device.SOLUTION: A liquid circulation device includes: a supply side manifold which supplies a liquid to a print bar equipped with one or more liquid discharge heads configured to discharge a liquid; a recovery side manifold which recovers the liquid from the print bar; and a bypass passage which allows the supply side manifold and the recovery side manifold to communicate with each other without passing through the print bar. In the liquid discharge head, the liquid is circulated by a differential pressure between the supply side manifold and the recovery side manifold. Resistance to the liquid can be changed in the bypass passage.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a liquid circulating device, a method for adjusting a liquid circulating device, and a method for manufacturing an image forming device, and more particularly to a technique for circulating liquid in a liquid ejection head. [Background technology]

[0002] Patent Document 1 describes a printing device having a flow path that bypasses the inkjet head in order to remove air bubbles in the supply flow path and the recovery flow path of the inkjet head having an ink circulation structure. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-099858 A Summary of the Invention [Problem to be solved by the invention]

[0004] [Challenge 1] In some cases, print bars including liquid ejection heads are modularized, and the number of print bars included in an image forming apparatus is variable. In a liquid supply system that uses pressure control, when the number of liquid ejection heads is changed, the flow rate of the entire apparatus changes.

[0005] However, when the amount of liquid circulating throughout the entire device changes, it becomes necessary to change the type of pump that supplies the liquid or to adjust parameters for controlling the pressure of the liquid. This is an issue.

[0006] [Challenge 2] In a circulation-type liquid ejection head, variations in the flow path resistance of the liquid ejection head cause variations in the amount of liquid circulating through the liquid ejection head, and the variation in the overall circulation amount becomes particularly large in a print bar that has multiple liquid ejection heads arranged in an array.

[0007] Meanwhile, abnormalities in the liquid supply system are detected, and deterioration of the pump is detected based on the operating state of the pump.

[0008] However, because the overall flow path resistance of the print bar varies depending on the individual liquid ejection head, the threshold for detecting an abnormality must be broadened, posing a problem in that small changes in the circulation amount cannot be detected.

[0009] The printing device described in Patent Document 1 cannot solve the first and second problems.

[0010] The present invention has been made in consideration of the above circumstances, and aims to provide a liquid circulation device, a method for adjusting a liquid circulation device, and a method for manufacturing an image forming device, which appropriately adjust the amount of liquid circulated, in order to solve at least one of the above-mentioned problems. [Means for solving the problem]

[0011] In order to achieve the above-mentioned object, a liquid circulation device according to a first aspect of the present disclosure includes a supply side manifold that supplies liquid to a print bar equipped with one or more liquid ejection heads that eject liquid, a recovery side manifold that recovers liquid from the print bar, and a bypass flow path that connects the supply side manifold and the recovery side manifold without passing through the print bar, the bypass flow path having changeable resistance to the liquid, and the liquid is circulated through the liquid ejection heads by the differential pressure between the supply side manifold and the recovery side manifold.

[0012] A liquid circulation device according to a second aspect of the present disclosure is the liquid circulation device according to the first aspect, wherein the print bar includes a plurality of liquid ejection heads, and the plurality of liquid ejection heads are preferably arranged along one direction.

[0013] A liquid circulation device according to a third aspect of the present disclosure is preferably such that, in the liquid circulation device according to the first or second aspect, when the maximum number of liquid ejection heads that can be mounted on a print bar is an integer n, the resistance of the bypass flow path is greater than or equal to 1 / n and less than or equal to 1 time the resistance of the liquid ejection head to the liquid.

[0014] A liquid circulation device according to a fourth aspect of the present disclosure is the liquid circulation device according to any one of the first to third aspects, wherein the resistance of the bypass flow path is preferably changed depending on the number of liquid ejection heads.

[0015] A liquid circulation device according to a fifth aspect of the present disclosure is the liquid circulation device according to any one of the first to fourth aspects, further comprising a pump that generates a pressure difference between the supply side manifold and the recovery side manifold, and it is preferable that the resistance of the bypass flow path is changed depending on the output value of the pump.

[0016] A liquid circulation device according to a sixth aspect of the present disclosure is the liquid circulation device according to any one of the first to fifth aspects, and preferably includes a flow meter for measuring a flow rate of liquid flowing through the supply side manifold, and the resistance of the bypass flow path is changed according to the measured flow rate.

[0017] A liquid circulation apparatus according to a seventh aspect of the present disclosure is the liquid circulation apparatus according to any of the first to sixth aspects, wherein the resistance of the bypass flow path is preferably changed to a value that brings the output value of the pump within ±5% of a predetermined output value.

[0018] A liquid circulation device according to an eighth aspect of the present disclosure is a liquid circulation device according to any one of the first to seventh aspects, further comprising a pump that generates a differential pressure between the supply side manifold and the recovery side manifold, and a flow meter that measures the amount of liquid flowing through the supply side manifold and / or the recovery side manifold, and it is preferable that the resistance of the bypass flow path is changed to a value that brings the flow rate of the liquid within ±5% of a predetermined flow rate.

[0019] A liquid circulation apparatus according to a ninth aspect of the present disclosure is the liquid circulation apparatus according to any one of the first to eighth aspects, further comprising an alarm device that notifies the user that a flow rate of the liquid flowing through the supply manifold has exceeded a predetermined threshold value, the threshold value being, for example, ±10% of the predetermined flow rate.

[0020] A liquid circulation device according to a tenth aspect of the present disclosure is the liquid circulation device according to any one of the first to ninth aspects, wherein the bypass flow path includes a bypass flow path valve, and the resistance of the bypass flow path is preferably changed by the bypass flow path valve.

[0021] In order to achieve the above-mentioned object, one aspect of a manufacturing method for an image forming apparatus according to an eleventh aspect of the present disclosure is a manufacturing method for an image forming apparatus including a print bar mounted with liquid ejection heads that eject liquid, where the maximum number of liquid ejection heads that can be mounted is an integer n, a supply side manifold that supplies liquid to the print bar, a recovery side manifold that recovers liquid from the print bar, a bypass flow path that connects the supply side manifold and the recovery side manifold without passing through the print bar, where the bypass flow path is capable of changing the resistance to the liquid, and a pump that generates a differential pressure in the supply side manifold and the recovery side manifold, where m is an integer greater than or equal to 1 and less than n, the manufacturing method includes the steps of mounting m liquid ejection heads on the print bar, and setting the resistance to 1 / (nm) of the resistance of the liquid ejection heads.

[0022] In order to achieve the above-mentioned object, a method for adjusting a liquid circulation device according to a twelfth aspect of the present disclosure is a method for adjusting a liquid circulation device including a supply side manifold that supplies liquid to a print bar equipped with a liquid ejection head that ejects liquid, a recovery side manifold that recovers liquid from the print bar, a bypass flow path that connects the supply side manifold and the recovery side manifold without passing through the print bar, the bypass flow path being capable of changing resistance to the liquid, and a pump that generates a differential pressure between the supply side manifold and the recovery side manifold, the method including closing the bypass flow path, measuring an output value of the pump, and setting the resistance in accordance with the output value. Effect of the Invention

[0023] According to the present invention, the amount of circulating liquid can be appropriately adjusted. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a diagram showing the configuration of an image forming apparatus. [Diagram 2] FIG. 2 is a configuration diagram of the liquid circulation device. [Diagram 3] FIG. 3 is a plan view perspective view showing an example of the structure of a liquid ejection head. [Figure 4] FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. [Diagram 5] FIG. 5 is a configuration diagram of the head module. [Figure 6] FIG. 6 is a diagram showing the configuration of the print bar. [Figure 7] FIG. 7 is a schematic diagram of a bypass flow path and a bypass flow path valve. [Figure 8] FIG. 8 is a conceptual diagram of the liquid circulated by the liquid circulating device. [Figure 9] FIG. 9 is a conceptual diagram of the liquid circulated by the liquid circulating device. [Figure 10] FIG. 10 is a conceptual diagram of the liquid circulated by the liquid circulating device. [Figure 11] FIG. 11 is a conceptual diagram of the liquid circulated by the liquid circulating device. [Figure 12] FIG. 12 is a configuration diagram of a liquid circulating device according to the second embodiment. [Figure 13] FIG. 13 is a graph showing the time variation of the output value of the supply side pump. [Figure 14] FIG. 14 is a configuration diagram of a liquid circulating device according to the third embodiment. [Figure 15] FIG. 15 is a functional block diagram showing the electrical configuration of the image forming apparatus. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0026] <Image forming device> 1 is a configuration diagram of an image forming apparatus 100. The image forming apparatus 100 prints (an example of "forming") an image on a web-like print medium 1 by a single pass method.

[0027] The printing medium 1 is, for example, general-purpose printing paper. General-purpose printing paper does not refer to so-called paper specifically for inkjet printing, but refers to paper that is mainly made of cellulose, such as coated paper used in general offset printing. The width of the printing medium 1 is the length in the direction perpendicular to the direction in which the printing medium 1 moves. The direction in which the printing medium 1 moves is the direction of the arrow in FIG. 1. The image forming apparatus 100 may be capable of printing on printing medium 1 of any width.

[0028] Moreover, images include photographs, pictures, characters, symbols, and the like.

[0029] As shown in FIG. 1, the image forming apparatus 100 includes a conveying device 120, a sending device 130, a pretreatment liquid applying device 140, a liquid applying device 150, a drying device 170, and a winding device 180.

[0030] [Transportation device] The transport device 120 transports the printing medium 1 along a transport path from the sending device 130 to the winding device 180. The transport device 120 corresponds to a movement mechanism that moves the printing medium 1 relatively to a liquid ejection head described later. The transport device 120 includes a plurality of pass rollers 122. The pass rollers 122 function as guide rollers that support the printing medium 1 on the transport path of the printing medium 1. The transport device 120 guides the printing medium 1 unwound from the sending device 130 with the plurality of pass rollers 122, and transports the printing medium 1 through the sending device 130, the pretreatment liquid application device 140, the liquid application device 150, the drying device 170, and the winding device 180 in this order.

[0031] [Delivery device] The delivery device 130 includes a delivery roll 132. The delivery roll 132 includes a rotatably supported reel (not shown). The print medium 1 before an image is printed is wound in a roll around the reel.

[0032] [Take-up device] The winding device 180 includes a winding roll 182. The winding roll 182 includes a rotatably supported reel (not shown). One end of the print medium 1 is connected to the reel. The winding roll 182 includes a winding motor (not shown) that drives the reel to rotate.

[0033] [Pretreatment Liquid Application Device] The pretreatment liquid application device 140 applies a pretreatment liquid to the printing surface of the printing medium 1. The pretreatment liquid is a liquid containing a component that thickens the aqueous liquid by aggregating or insolubilizing coloring material components in the aqueous liquid. The pretreatment liquid application device 140 includes an application roller 142, a counter roller 144, and a pretreatment liquid drying device 146. The printing medium 1 conveyed from the delivery device 130 is guided by a path roller 122 and conveyed to a position facing the application roller 142. The pretreatment liquid application device 140 sandwiches the printing medium 1 between the application roller 142, the outer circumferential surface of which is supplied with pretreatment liquid, and the counter roller 144, and applies the pretreatment liquid on the outer circumferential surface of the application roller 142 to the printing surface of the printing medium 1. The pretreatment liquid drying device 146 performs a drying process on the printing medium 1 to which the pretreatment liquid has been applied. The pretreatment liquid drying device 146 blows hot air onto the printing medium 1 by a hot air heater (not shown).

[0034] [Liquid application device] Liquid application device 150 applies liquid to the printing surface of print medium 1 to print a color image. Liquid application device 150 includes print bars 40K, 40C, 40M, 40Y, and 40W. Print bars 40K, 40C, 40M, 40Y, and 40W eject black, cyan, magenta, yellow, and white liquids, respectively. Print bars 40, which will be described later, can be used as print bars 40K, 40C, 40M, 40Y, and 40W.

[0035] The liquid used in the liquid application device 150 is ink for image formation. The ink may be a water-based ink, a UV-curable ink, etc. The ink may be low-viscosity or high-viscosity.

[0036] Liquid application device 150 includes liquid circulating devices 10K, 10C, 10M, 10Y, and 10W. Liquid circulating devices 10K, 10C, 10M, 10Y, and 10W may be liquid circulating devices 10, 10A, or 10B, which will be described later. Liquid circulating devices 10K, 10C, 10M, 10Y, and 10W circulate liquids of corresponding colors through print bars 40K, 40C, 40M, 40Y, and 40W, respectively.

[0037] The liquid application device 150 includes a print drum 152 and a scanner 154. The print drum 152 includes suction holes (not shown) on its outer circumferential surface. The print drum 152 sucks the print medium 1 from the inside through the suction holes to adhere it to its outer circumferential surface, and transports the print medium 1 by rotating. The liquid application device 150 prints a color image on the printing surface of the print medium 1 by ejecting liquid of each color from print bars 40K, 40C, 40M, 40Y, and 40W onto the print medium 1 transported directly below by the print drum 152.

[0038] The scanner 154 includes an imaging device that captures an image, such as a test image, printed on the printing surface of the print medium 1 and generates an imaging signal corresponding to the image. As the imaging device, a color CCD (Charge Coupled Device) linear image sensor or a color CMOS (Complementary Metal Oxide Semiconductor) linear image sensor can be used.

[0039] [Drying equipment] The drying device 170 includes a drying drum 172. The drying drum 172 includes suction holes (not shown) on its outer circumferential surface. The drying drum 172 sucks the print medium 1 from the inside through the suction holes to adsorb the print medium 1 to its outer circumferential surface, and conveys the print medium 1 by rotating. The drying device 170 blows hot air from a hot air heater (not shown) toward the print surface of the print medium 1 conveyed by the drying drum 172, thereby drying the print surface of the print medium 1.

[0040] First Embodiment [Liquid circulation device] Fig. 2 is a configuration diagram of the liquid circulation device according to the first embodiment. Liquid circulation device 10 is a device that circulates liquid to print bar 40. As shown in Fig. 2, liquid circulation device 10 includes a liquid tank 12, a supply side flow path 14, a recovery side flow path 16, joints 18I and 18O, a supply side back pressure tank 28, a supply side pressure sensor 31, a recovery side pressure sensor 62, and a recovery side back pressure tank 64.

[0041] The liquid tank 12 stores the liquid to be circulated through the liquid circulation device 10. The liquid tank 12 includes a supply port 12A and a recovery port 12B. The supply port 12A is connected to a supply-side flow path 14, and the recovery port 12B is connected to a recovery-side flow path 16.

[0042] The supply side flow path 14 distributes the liquid from the liquid tank 12 to the liquid circulation device 10. The recovery side flow path 16 distributes the liquid from the liquid tank 12 to the liquid circulation device 10.

[0043] The supply-side flow path 14 and the recovery-side flow path 16 are configured to include flow path components such as tubes. The supply-side flow path 14 communicates between the liquid tank 12 and the liquid circulation device 10 via a joint 18I. The recovery-side flow path 16 communicates between the liquid circulation device 10 and the liquid tank 12 via a joint 18O.

[0044] A degassing module 22, a supply-side pump 24, and a supply-side filter 26 are connected to the supply-side flow path 14 by joints 20, respectively.

[0045] The degassing module 22 performs a degassing process on the liquid passing through the supply side flow path 14 .

[0046] The supply-side pump 24 applies pressure to the liquid inside the supply-side flow path 14, causing the liquid inside the supply-side flow path 14 to flow, and supplies the liquid stored in the liquid tank 12 to the liquid circulation device 10. A tube pump, for example, can be used as the supply-side pump 24. The supply-side filter 26 removes air bubbles, foreign matter, and the like contained in the liquid.

[0047] The output value of the supply pump 24 has a fixed relationship with the amount of liquid supplied to the supply flow path 14. The output value of the supply pump 24 is the number of revolutions of the supply pump 24 per unit time. The supply pump 24 is configured so that the output value can be monitored. The fixed relationship may be a direct proportional relationship or a direct correlation relationship.

[0048] A recovery pump 66 and a recovery filter 68 are provided in the recovery flow path 16 by joints 20 .

[0049] The recovery pump 66 applies pressure to the liquid inside the recovery flow path 16, causing the liquid inside the recovery flow path 16 to flow, and recovers the liquid supplied to the liquid circulation device 10 into the liquid tank 12. A tube pump, for example, can be used as the recovery pump 66. The recovery filter 68 removes air bubbles, foreign matter, and the like contained in the liquid.

[0050] The output value of the recovery pump 66 has a fixed relationship with the amount of liquid recovered from the recovery flow path 16. The output value of the recovery pump 66 is the number of rotations of the recovery pump 66 per unit time. The recovery pump 66 is configured so that the output value can be monitored. The fixed relationship may be a direct proportional relationship or a direct correlation relationship.

[0051] Furthermore, a one-way valve 72 is provided in the recovery flow path 16. The one-way valve 72 allows the liquid to flow only from the liquid circulation device 10 side to the liquid tank 12 side, and restricts the liquid to flow from the liquid tank 12 side to the liquid circulation device 10 side.

[0052] Supply-side back-pressure tank 28 is a pressure buffer device that suppresses fluctuations in the internal pressure of supply-side flow path 14 and liquid circulation device 10. Supply-side back-pressure tank 28 includes liquid inlet 28A, liquid outlet 28B, liquid chamber 28C, air chamber 28D, and elastic membrane 28E.

[0053] Supply-side back pressure tank 28 communicates with supply-side flow path 14 via liquid inlet 28A and joint 18I. Supply-side back pressure tank 28 also communicates with liquid circulating device 10 via liquid outlet 28B. The liquid that flows in from liquid inlet 28A flows out from liquid outlet 28B via liquid chamber 28C.

[0054] Air is sealed in air chamber 28D. Elastic membrane 28E is disposed between liquid chamber 28C and air chamber 28D to separate liquid chamber 28C from air chamber 28D. Elastic membrane 28E deforms in response to pressure fluctuations of the liquid passing through liquid chamber 28C, reducing pressure fluctuations of the liquid passing through liquid chamber 28C.

[0055] The liquid exiting the liquid outlet 28B flows into the supply manifold 30.

[0056] The recovery-side back pressure tank 64 is a pressure buffer device that suppresses fluctuations in the internal pressure of the liquid circulation system 10. The configuration of the recovery-side back pressure tank 64 is similar to the configuration of the supply-side back pressure tank 28. The liquid that has flowed into the liquid circulation system 10 flows out of the liquid circulation system 10 via the recovery-side back pressure tank 64 and the joint 18O.

[0057] The liquid circulation device 10 includes a supply manifold 30, liquid supply channels 32-1, 32-2, ..., 32-n, liquid ejection heads 34-1, 34-2, ..., 34-n, liquid recovery channels 36-1, 36-2, ..., 36-n, bypass channels 38, a print bar 40, and a recovery manifold 60. The multiple liquid supply channels 32-1, 32-2, ..., 32-n are also referred to as liquid supply channels 32 when not distinguished from one another. The multiple liquid ejection heads 34-1, 34-2, ..., 34-n are also referred to as liquid ejection heads 34 when not distinguished from one another. The multiple liquid recovery channels 36-1, 36-2, ..., 36-n are also referred to as liquid recovery channels 36 when not distinguished from one another.

[0058] The print bar 40 is a line-type head having a structure in which a plurality of liquid ejection heads 34-1, 34-2, ..., 34-n, each of which ejects liquid, are connected in one direction. The liquid ejection heads 34-1, 34-2, ..., 34-n may be arranged linearly in one direction, or may be arranged in a zigzag pattern in one direction. The print bar 40 may be composed of only one liquid ejection head 34.

[0059] Each of the liquid ejection heads 34-1, 34-2, ..., 34-n has a liquid supply port 41A and a liquid recovery port 41B. The print bar 40 has liquid supply channels 32-1, 32-2, ..., 32-n. The liquid supply ports 41A of the liquid ejection heads 34-1, 34-2, ..., 34-n are connected to the liquid supply channels 32-1, 32-2, ..., 32-n, respectively. The supply manifold 30 is connected to the liquid supply ports 41A of the liquid ejection heads 34-1, 34-2, ..., 34-n, respectively, via the liquid supply channels 32-1, 32-2, ..., 32-n. The liquid that flows into the supply manifold 30 flows into the liquid ejection heads 34-1, 34-2, ..., 34-n via the liquid supply ports 41A.

[0060] Each of the liquid supply channels 32-1, 32-2, ..., 32-n includes a supply valve (not shown) and a supply damper (not shown). The supply valve switches between communication and blocking of each of the liquid supply channels 32-1, 32-2, ..., 32-n. The supply damper absorbs pressure fluctuations of the liquid flowing through the liquid supply channels 32-1, 32-2, ..., 32-n.

[0061] The print bar 40 has liquid recovery flow paths 36-1, 36-2, ..., 36-n. The liquid recovery ports 41B of the liquid ejection heads 34-1, 34-2, ..., 34-n are connected to the liquid recovery flow paths 36-1, 36-2, ..., 36-n, respectively. The recovery manifold 60 is connected to the liquid recovery ports 41B of the liquid ejection heads 34-1, 34-2, ..., 34-n, respectively, via the liquid recovery flow paths 36-1, 36-2, ..., 36-n.

[0062] The liquid that has flowed into the liquid ejection heads 34-1, 34-2, . . . , 34-n flows into the recovery manifold 60 via liquid recovery flow paths 36-1, 36-2, . . . , 36-n.

[0063] Each of the liquid recovery channels 36-1, 36-2, ..., 36-n is equipped with a recovery damper (not shown) and a recovery valve (not shown). The recovery damper absorbs pressure fluctuations of the liquid flowing through the liquid recovery channels 36-1, 36-2, ..., 36-n. The recovery valve switches between communication and cut-off of each of the liquid recovery channels 36-1, 36-2, ..., 36-n.

[0064] The bypass flow path 38 connects the supply manifold 30 and the recovery manifold 60 without passing through the print bar 40. A plurality of bypass flow paths 38 may be provided. Each bypass flow path 38 is provided with a bypass flow path valve 42 that opens and closes the bypass flow path 38. When a plurality of bypass flow paths 38 are provided, each bypass flow path 38 may be provided with a bypass flow path valve 42.

[0065] The supply side pressure sensor 31 detects the internal pressure of the supply side manifold 30. The supply side pressure sensor 31 can be a semiconductor piezoresistance type, a capacitance type, a silicon resonant type, or the like sensor.

[0066] The recovery side pressure sensor 62 detects the internal pressure of the recovery side manifold 60. As with the supply side pressure sensor 31, the recovery side pressure sensor 62 may be a sensor of a semiconductor piezoresistance type, a capacitance type, a silicon resonant type, or the like.

[0067] In the liquid circulation system 10 configured as described above, a pressure is set in the supply manifold 30 by the supply pump 24. Also, a pressure is set in the recovery manifold 60 by the recovery pump 66. The pressure set in the supply manifold 30 is relatively higher than the pressure set in the recovery manifold 60. The difference between the pressure set in the supply manifold 30 and the pressure set in the recovery manifold 60 is the differential pressure.

[0068] The liquid circulation device 10 circulates liquid to a plurality of liquid ejection heads 34 using the differential pressure between the supply manifold 30 and the recovery manifold 60. The liquid circulation device 10 sets the amount of liquid circulated to each liquid ejection head 34 depending on the value of the differential pressure.

[0069] [Liquid ejection head] Fig. 3 is a planar perspective view showing an example of the structure of a liquid ejection head. As shown in Fig. 3, the liquid ejection head 34 includes a plurality of nozzles 202. The plurality of nozzles 202 are arranged two-dimensionally. Note that the arrangement of the nozzles 202 is not limited to two-dimensionally.

[0070] The plurality of nozzles 202 each communicate with a pressure chamber 204. The pressure chamber 204 communicates with a supply branch 210. The supply branch 210 communicates with a common flow path 212. The common flow path 212 communicates with the liquid supply port 41A.

[0071] Further, each nozzle 202 communicates with a recovery branch 218 via a liquid circulation path 216 (see FIG. 4). The recovery branch 218 communicates with a common circulation path 220. The common circulation path 220 communicates with the liquid recovery port 41B.

[0072] Fig. 4 is a cross-sectional view taken along line 4-4 of Fig. 3. As shown in Fig. 4, the liquid ejection head 34 includes a nozzle plate 230, a flow path plate 232, and an actuator 228. The liquid ejection head 34 has a structure in which the nozzle plate 230, the flow path plate 232, and the actuator 228 are laminated in this order.

[0073] A plurality of nozzles 202 are formed in the nozzle plate 230. The nozzles 202 have openings formed in the nozzle surface 200 and have a structure penetrating the nozzle plate 230.

[0074] In the flow path plate 232, a pressure chamber 204, a supply restrictor 208, a supply branch 210, a common flow path 212, a descender 214, a liquid circulation path 216, a recovery branch 218, and a circulation common flow path 220 are formed.

[0075] The nozzle 202 communicates with a pressure chamber 204 via a descender 214. The pressure chamber 204 communicates with a supply tributary 210 via a supply restriction 208. The nozzle 202 also communicates with a return tributary 218 via a liquid circulation path 216.

[0076] The liquid flows through the common flow path 212, the supply tributary 210, the supply restrictor 208, the pressure chamber 204, and the descender 214, and a portion of the liquid is ejected from each nozzle 202. The liquid that is not ejected from the nozzles 202 is discharged via the liquid circulation path 216, the recovery tributary 218, and the circulation common flow path 220.

[0077] It is preferable that the liquid circulation path 216 is arranged around the nozzle 202. Here, the liquid circulation path 216 is an area that communicates with the descender 214, and is arranged in an area of ​​the flow path plate 232 that contacts the nozzle plate 230. This allows the liquid to circulate in the vicinity of the nozzle 202, suppresses thickening of the liquid inside the nozzle 202, and realizes stable ejection from the liquid ejection head 34.

[0078] The actuator 228 is disposed on the diaphragm 226 which is the top surface of the pressure chamber 204 and also serves as a common electrode. The actuator 228 is a piezoelectric element including a piezoelectric layer (not shown) and individual electrodes (not shown).

[0079] The actuator 228 is deflected in response to application of a drive voltage to the individual electrodes. The deformation of the actuator 228 causes the pressure chamber 204 to deform, and in response to the contraction of the pressure chamber 204, liquid is ejected from the nozzle 202. In addition, in response to the expansion of the pressure chamber 204 after the liquid is ejected from the nozzle 202, new liquid is supplied to the pressure chamber 204 from the common flow path 212 through the supply tributary 210 and the supply orifice 208.

[0080] Although a piezoelectric method has been exemplified as a liquid ejection method here, a thermal method or an electrostatic method may also be used as the liquid ejection method.

[0081] [Head module] A plurality of liquid ejection heads 34 may constitute one head module. Fig. 5 is a configuration diagram of a head module. The head module 21 shown in Fig. 5 includes four liquid ejection heads 34. The four liquid ejection heads 34 are each connected to a liquid supply flow path 32 and a liquid recovery flow path 36. The four liquid ejection heads 34 may be arranged in a zigzag pattern. The number of liquid ejection heads 34 included in the head module 21 is not limited to four.

[0082] Fig. 6 is a configuration diagram of a print bar. The print bar 40 shown in Fig. 6 includes four head modules 21. The head modules 21 may be arranged in a zigzag pattern. Note that the number of head modules 21 included in the print bar 40 is not limited to four.

[0083] The liquid circulation device 10 can expand the print bar 40 by connecting the head modules 21 in the X direction. The use of the head modules 21 in the liquid circulation device 10 facilitates maintenance and design work. As the print bar 40 expands, the length of the supply side manifold 30 and the recovery side manifold 60 in the X direction may be changeable, and the supply side manifold 30 and the recovery side manifold 60 may be expandable in the X direction. Furthermore, the supply side manifold 30 and the recovery side manifold 60 may have a structure in which multiple manifolds are used in series or in parallel.

[0084] [Resistance of bypass flow path] 7 is a schematic diagram of the bypass flow passage 38 and the bypass flow passage valve 42. The bypass flow passage valve 42 changes the resistance of the bypass flow passage 38 by changing the cross-sectional area of ​​the bypass flow passage 38. The resistance is the resistance that a liquid receives from a pipeline when the liquid is caused to flow through the pipeline, and is also called flow passage resistance. The bypass flow passage valve 42 may be operated in response to a control signal or may be operated by being manually operated. The bypass flow passage valve 42 may be a needle-shaped valve.

[0085] Changing the cross-sectional area of ​​the bypass flow path 38 to 0 times the maximum cross-sectional area of ​​the bypass flow path 38 means that the bypass flow path 38 is completely closed, and the flow path resistance becomes infinite. Changing the cross-sectional area of ​​the bypass flow path 38 to 1 time the maximum cross-sectional area of ​​the bypass flow path 38 means that the bypass flow path 38 is completely opened. This makes it possible to change the resistance of the bypass flow path 38, and therefore the amount of liquid flowing through the bypass flow path 38.

[0086] During maintenance work or when filling the liquid ejection heads 34-1, 34-2, ..., 34-16 with liquid, the bypass flow path 38 may have the bypass flow path valve 42 opened to remove air bubbles. During printing, the bypass flow path 38 may have the bypass flow path valve 42 closed.

[0087] In addition, when the liquid circulation device 10 has multiple bypass flow paths 38, it is sufficient that at least one of the bypass flow paths 38 is provided with a bypass flow path valve 42 capable of changing the resistance, and the other bypass flow paths 38 are provided with valves that only open and close the bypass flow paths 38.

[0088] [Relationship between the number of printbar head modules and the resistance of the bypass flow path] 8, 9, 10 and 11 are conceptual diagrams relating to the liquid circulated by the liquid circulating device 10. FIG.

[0089] 8 to 11, Pdiff indicates the differential pressure applied to each liquid ejection head 34 and each bypass flow path 38 due to the pressure of the supply pump 24 (see FIG. 2) and the pressure of the recovery pump 66 (see FIG. 2), and is a constant value here. Vtotal is the total amount of liquid flowing through each liquid ejection head 34 and each bypass flow path 38. Rh1, Rh2, Rh3, . . . , Rh16 are the resistances of the liquid ejection heads 34-1, 34-2, 34-3, . . . , 34-16 to the liquid, respectively. The resistances of the liquid ejection heads 34-1, 34-2, 34-3, . . . , 34-16 are the resistances between the supply manifold 30 (see FIG. 2) and the recovery manifold 60 (see FIG. 2), and include the resistances of the liquid supply flow path 32 (see FIG. 2), the liquid recovery flow path 36 (see FIG. 2), and the connectors connecting the flow paths, etc.

[0090] 8 to 11, since the liquid circulation device 10 has a plurality of liquid ejection heads 34 connected in parallel, the amount of liquid circulating through each liquid ejection head 34 does not depend on the resistance of the bypass flow paths 38, 38-1, and 38-2, but is determined only by Pdiff. On the other hand, Vtotal is affected by the resistance of the bypass flow paths 38, 38-1, and 38-2.

[0091] Vh1, Vh2, Vh3, ..., Vh16 are the amounts of liquid circulating through the liquid ejection heads 34-1, 34-2, 34-3, ..., 34-16, respectively. Rb, Rb1, Rb2 are the resistances to the liquid in the bypass flow paths 38, 38-1, 38-2, respectively. Vb, Vb1, Vb2 are the amounts of liquid flowing through the bypass flow paths 38, 38-1, 38-2, respectively.

[0092] FIG. 8 shows a case where one bypass flow path 38 is provided and 16 liquid ejection heads 34-1, 34-2, . . . , 34-16 are connected. That is, FIG. 8 shows a state where four head modules 21 (see FIG. 5) are connected. FIG. 8 shows a state where the bypass flow path valve 42 (see FIG. 2) is closed. That is, FIG. 8 shows a case where Rb is infinite and Vb is 0, that is, liquid is not flowed through the bypass flow path 38. In this case, if the average value of Vh1, Vh2, Vh3, . . . , Vh16 is Vh_ave, Vtotal is 16 times Vh_ave. Note that the average value of Rh1, Rh2, Rh3, . . . , Rh16 is Rh_ave.

[0093] Fig. 9 shows a case where four liquid ejection heads 34-1, 34-2, 34-3, and 34-4 are connected to one bypass flow path 38. That is, Fig. 9 shows a state where one head module 21 is connected.

[0094] 8 and 9, the number of liquid ejection heads 34 is different, but Vtotal is considered to be maintained when Pdiff is constant. That is, it is desired to make Vtotal in FIG. 9 the same value as Vtotal in FIG.

[0095] In this case, Rb should be set to 1 / 12 of Rh_ave. As a result, Vb becomes 12 times Vh_ave, and Vtotal can be adjusted to the Vtotal in FIG.

[0096] Fig. 10 shows a case where eight liquid ejection heads 34-1, 34-2, ..., 34-8 are connected to one bypass flow path 38. That is, Fig. 10 shows a state where two head modules 21 are connected.

[0097] 9, when Pdiff is constant, Vtotal is considered to be the same as in FIG. 8. That is, it is desired that Vtotal in FIG. 10 be the same value as Vtotal in FIG.

[0098] In this case, Rb should be set to 1 / 8 of Rh_ave. As a result, Vb becomes 8 times Vh_ave, and Vtotal can be adjusted to the Vtotal in FIG.

[0099] Thus, if n is an integer and m is an integer greater than or equal to 1 and less than n, and if m liquid ejection heads 34 are mounted on a print bar 40 whose maximum number of mountable liquid ejection heads 34 is n (here, n=16), then Rb should be set to 1 / (nm) times Rh_ave.

[0100] 11 shows a case where two bypass flow paths 38-1, 38-2 are provided and four liquid ejection heads 34-1, 34-2, ..., 34-4 are connected. As in the past, when Pdiff is constant, Vtotal is considered to be the same as in FIG. 8. That is, it is desired to set Vtotal in FIG. 11 to the same value as Vtotal in FIG. 8.

[0101] Here, as an example, Rb1 and Rb2 may be set to 1 / 8 and 1 / 4 times Rh_ave, respectively. As a result, Vb1 and Vb2 become 8 and 4 times Vh_ave, respectively, and Vtotal can be matched to Vtotal in the case of Fig. 8. In other words, when there are multiple bypass flow paths 38, the resistance of each bypass flow path 38 may be set so that the combined resistance of the bypass flow paths 38 is 1 / (nm) times Rh_ave.

[0102] In this way, when liquid is flowed through the bypass flow path 38, the resistance of the bypass flow path 38 is 1 / n to 1 times the resistance of the liquid ejection heads 34 to the liquid, where n is the maximum number of liquid ejection heads 34 that can be mounted.

[0103] Here, an example has been described in which Vtotal is set to the reference value when the maximum number (16) of mountable liquid ejection heads 34 are mounted on the print bar 40 and liquid is not flowed through the bypass flow path 38, and Vtotal is maintained when the number of liquid ejection heads 34 is changed, but Vtotal may also be set to the reference value when the maximum number of mountable liquid ejection heads 34 are mounted on the print bar 40 and a constant amount of liquid is flowed through the bypass flow path 38. In this case as well, Vtotal can be maintained even when the number of liquid ejection heads 34 is changed by adjusting the resistance of the bypass flow path.

[0104] In addition, the resistance generated in the liquid supply flow path 32, the liquid recovery flow path 36, and the connectors connecting the flow paths can be ignored by making the resistance relatively smaller than the resistance of the liquid ejection head 34 by, for example, increasing the inner diameter of the tubes or using connectors with low resistance.

[0105] Furthermore, if the resistance of the bypass flow passage 38 is relatively small, the amount of liquid flowing through the bypass flow passage 38 becomes relatively large. As a result, the accuracy of pressure control may decrease due to fluctuations in pressure loss. In that case, the amount of liquid circulating through the liquid circulation device 10 can be made constant by providing multiple bypass flow passages 38 and adjusting the resistance of each bypass flow passage 38. The resistances of the multiple bypass flow passages 38 may be calculated as a single combined resistance.

[0106] According to the liquid circulation device 10, by changing the resistance of the bypass flow path 38 so that the circulation amount of the liquid flowing through the liquid circulation device 10 is constant with the same pressure setting, it is possible to achieve the effect of eliminating the need to change parameters for pressure control, pump control, and temperature control even when the number of head modules 21 is changed. In other words, by changing the resistance of the bypass flow path 38 in accordance with the number of liquid ejection heads 34, the circulation amount of the liquid flowing through the liquid circulation device 10 can be adjusted to an appropriate value.

[0107] <Second embodiment> [Changes in circulating volume] The amount of liquid circulated by liquid circulating device 10 may fluctuate due to an abnormality in the liquid supply system or deterioration of the pump.

[0108] Furthermore, the operating states of the supply-side pump 24 and the recovery-side pump 66 may be detected in order to detect fluctuations in the amount of liquid circulating in the liquid circulating device 10. For example, if the supply-side pump 24 and the recovery-side pump 66 are tube pumps, the rotation speed of the tube pumps is measured to detect fluctuations in the amount of liquid circulating.

[0109] When the supply pump 24 or the recovery pump 66 deteriorates, the circulation amount relative to the rotation speed decreases. Therefore, when the circulation amount is controlled to be constant, the rotation speed of the pump increases, and the circulation amount appears to increase.

[0110] On the other hand, cases where the amount of liquid circulated by the liquid circulating device 10 actually increases include liquid leakage, a decrease in the viscosity of the liquid, etc. Cases where the amount of liquid circulated by the liquid circulating device 10 actually decreases include the generation of air bubbles in the circulation flow path, clogging, an increase in the viscosity of the liquid, etc.

[0111] [Configuration of the liquid circulation device] Fig. 12 is a configuration diagram of a liquid circulating apparatus according to the second embodiment. As shown in Fig. 12, a liquid circulating apparatus 10A includes a flow meter 80. The other configurations are similar to those of the liquid circulating apparatus 10 shown in Fig. 2 and are not shown in the figure.

[0112] The flowmeter 80 measures the amount of liquid circulating through the liquid circulation apparatus 10A. That is, the flowmeter 80 measures the amount of liquid flowing through the supply manifold 30 and / or the recovery manifold 60. The measurement method of the flowmeter 80 may be ultrasonic, electromagnetic, Coriolis, thermal, Karman vortex, impeller, float, or differential pressure. The flowmeter 80 may store the measurement results as data. The data may be computer-readable. The stored data may be used after being subjected to statistical processing or the like.

[0113] [Method of Adjusting the Liquid Circulation Device] The adjustment method for liquid circulation apparatus 10A adjusts the output value of supply-side pump 24 and the output value of recovery-side pump 66 to within ±5%, preferably ±1%, of a preset value.

[0114] Fig. 13 is a graph showing the time variation of the output value of the supply-side pump 24. In Fig. 13, the vertical axis shows the number of revolutions per unit time of the supply-side pump 24 in units of [rpm (revolutions per minute)]. Also, in Fig. 13, the horizontal axis shows time in units of [minutes]. That is, the output value of the supply-side pump 24 is the number of revolutions per unit time of the supply-side pump 24. Here, the number of revolutions per unit time of the supply-side pump 24 is set to 1000 rpm, and the threshold values ​​set to issue a warning are an upper limit threshold of 1200 rpm and a lower limit threshold of 800 rpm.

[0115] In the example shown in Fig. 13, the rotation speed per unit time of the supply-side pump 24 is about 900 rpm, which is lower than the set value. In this case, since the rotation speed per unit time of the supply-side pump 24 is close to the lower limit threshold, a lower limit warning is likely to be issued. On the other hand, since the rotation speed per unit time of the supply-side pump 24 is far from the upper limit threshold, an upper limit warning is unlikely to be issued. For this reason, it has not been easy to detect an abnormality from the rotation speed per unit time of the supply-side pump 24.

[0116] Returning to the explanation of Fig. 12, a method of adjusting liquid circulation apparatus 10A will be explained taking as an example a case where print bar 40 includes 16 liquid ejection heads 34 and one bypass flow path 38. When bypass flow path 38 is closed by bypass flow path valve 42 and the rotation speeds of supply side pump 24 and recovery side pump 66 are both set to 1000 rpm, it is assumed that the actual output values ​​of supply side pump 24 and recovery side pump 66 are both 900 rpm. In this case, it is considered that the resistance of each liquid ejection head 34 is higher than expected, and therefore the output values ​​of supply side pump 24 and recovery side pump 66 are smaller than the set values.

[0117] Here, in order to adjust the rotation speeds of the supply-side pump 24 and the recovery-side pump 66 to 1000 rpm, the resistance of the bypass flow path 38 should be set so that liquid equivalent to 100 rpm flows through the bypass flow path 38. In other words, since the circulation amount per one liquid ejection head 34 is equivalent to approximately 60 rpm, the resistance of the bypass flow path 38 should be set to 60 / 100 of the resistance of one liquid ejection head 34.

[0118] Here, approximate resistance values ​​are shown, but by changing and adjusting the resistance of the bypass flow path 38 when the liquid temperature, etc. are in a steady state, the rotation speeds of the supply side pump 24 and the recovery side pump 66 can be adjusted to the target set value of 1000 rpm.

[0119] Although the pump rotation speed is used as the output value here, the amount of liquid circulating through liquid circulation apparatus 10A may also be used as the output value. The amount of liquid circulating through liquid circulation apparatus 10A is measured by flowmeter 80. By using flowmeter 80, it is possible to distinguish between deterioration of supply-side pump 24 and recovery-side pump 66 and other malfunctions.

[0120] Thus, the method for adjusting the liquid circulation apparatus 10A includes the step of closing the bypass flow path 38. Closing the bypass flow path 38 is synonymous with closing the bypass flow path valve 42 and making the resistance of the bypass flow path 38 infinite.

[0121] The method for adjusting liquid circulation apparatus 10A also includes a step of measuring the output values ​​of the pumps. The output values ​​of the pumps are, for example, the output value of supply-side pump 24 and the output value of recovery-side pump 66. The output values ​​of supply-side pump 24 and the output value of recovery-side pump 66 are, for example, the number of rotations per unit time. Instead of the output values ​​of the pumps, the amount of liquid circulating through liquid circulation apparatus 10A may be measured.

[0122] Furthermore, the method for adjusting the liquid circulation device 10A includes a setting step of setting the resistance in accordance with the measured output value. The setting step may set the resistance based on the number of liquid ejection heads 34 that circulate the liquid.

[0123] The adjustment method for liquid circulation apparatus 10A is preferably performed when print bar 40 begins to be used, when liquid ejection head 34 is replaced, when supply pump 24 is replaced, or when recovery pump 66 is replaced.

[0124] According to the adjustment method of the liquid circulation apparatus 10A, the output value of the supply-side pump 24 and the output value of the recovery-side pump 66 can be adjusted to within ±5%, preferably ±1%, of a preset value without changing other parameters, resulting in an effect of narrowing the range of the threshold for detecting an abnormality.

[0125] <Third embodiment> The liquid circulation device according to the third embodiment detects an abnormality in the liquid circulation device by detecting when the output value of the pump exceeds preset upper and lower limits. Here, as an example, the output value of the pump is detected using the flow rate of the liquid circulating through the liquid circulation device.

[0126] [Configuration of the liquid circulation device] 14 is a configuration diagram of a liquid circulation apparatus according to the third embodiment. As shown in Fig. 14, a liquid circulation apparatus 10B includes an alarm device 90. The other configuration is similar to that of the liquid circulation apparatus 10A shown in Fig. 12.

[0127] The notification device 90 is connected to the flowmeter 80. The notification device 90 notifies that the flow rate has exceeded a predetermined threshold based on the measurement result of the flowmeter 80. The threshold is, for example, ±20% of the predetermined flow rate, and preferably ±10%. The notification device 90 notifies users, such as a design worker, people in the vicinity, or a worker performing printing or maintenance work, by displaying a warning on a screen, emitting a warning sound, outputting a log related to the warning, sending an email related to the warning via a communication line, or the like.

[0128] The upper limit of the flow rate is desirably set to a value that is +5% of a preset value, preferably +1%. The lower limit of the flow rate is desirably set to a value that is -5% of a preset value, preferably -1%. When the flow rate reaches the threshold value, the notification device 90 issues a warning. The liquid circulation device 10B has the effect of being able to notify the user of an abnormality in the liquid circulation device 10.

[0129] Here, the notification device 90 notifies that the flow rate has exceeded a threshold value, but may also notify that the rotation speed per unit time of the supply-side pump 24 has exceeded a threshold value.

[0130] <Manufacturing method of image forming apparatus> The manufacturing method for image forming apparatus 100 includes a print bar 40 equipped with liquid ejection heads 34 that eject liquid, where the maximum number of liquid ejection heads 34 that can be mounted is an integer n, a supply side manifold 30 that supplies liquid to the print bar 40, a recovery side manifold 60 that recovers liquid from the print bar 40, a bypass flow path 38 that connects the supply side manifold 30 and the recovery side manifold 60 without passing through the print bar 40, where the bypass flow path 38 has an adjustable resistance to the liquid, and a supply side pump 24 that generates a differential pressure between the supply side manifold 30 and the recovery side manifold 60.

[0131] Furthermore, the manufacturing method for image forming apparatus 100 includes a step of mounting m liquid ejection heads 34 on print bar 40, where m is an integer equal to or greater than 1 and less than n. That is, the user mounts m liquid ejection heads 34 on print bar 40 and connects print bar 40 to liquid circulation device 10. The number of liquid ejection heads 34 may be determined in accordance with the width of print medium 1. The user may mount liquid ejection heads 34 in units of head modules 21.

[0132] Furthermore, the manufacturing method of the image forming apparatus 100 includes a step of setting the resistance of the bypass flow path 38 to 1 / (nm) of the resistance of the liquid ejection head. That is, the user sets the resistance of the bypass flow path 38 to 1 / (nm) of the resistance of the liquid ejection head by the bypass flow path valve 42. The resistance of the liquid ejection head may be the average value of the resistances of the multiple liquid ejection heads 34. When multiple bypass flow paths 38 are provided, the user may set the combined resistance of the multiple bypass flow paths 38 to 1 / (nm) of the resistance of the liquid ejection head.

[0133] <Electrical configuration of the image forming apparatus> 15 is a functional block diagram showing the electrical configuration of the image forming apparatus. The image forming apparatus 100 includes a control device 95. The control device 95 includes a processor 96 and a memory 98. The control device 95 controls the bypass flow passage valve 42, the supply side pump 24, and the recovery side pump 66 of the liquid circulation device 10. The control device 95 may also control the notification device 90. The control device 95 also acquires the measurement result of the flow meter 80.

[0134] The hardware structure of the processor 96 is various processors as shown below. The various processors include a CPU (Central Processing Unit), which is a general-purpose processor that executes software (programs) and acts as various functional units, a GPU (Graphics Processing Unit), which is a processor specialized for image processing, a PLD (Programmable Logic Device), which is a processor whose circuit configuration can be changed after manufacture such as an FPGA (Field Programmable Gate Array), and a dedicated electric circuit, which is a processor having a circuit configuration designed specifically for executing specific processing such as an ASIC (Application Specific Integrated Circuit).

[0135] One processing unit may be configured with one of these various processors, or may be configured with two or more processors of the same or different types (for example, multiple FPGAs, or a combination of a CPU and an FPGA, or a combination of a CPU and a GPU). Also, multiple functional units may be configured with one processor. As an example of configuring multiple functional units with one processor, first, as represented by a computer such as a client or a server, there is a form in which one processor is configured with a combination of one or more CPUs and software, and this processor acts as multiple functional units. Second, as represented by a SoC (System On Chip), there is a form in which a processor is used that realizes the functions of the entire system including multiple functional units with one IC (Integrated Circuit) chip. In this way, the various functional units are configured using one or more of the above various processors as a hardware structure.

[0136] Furthermore, the hardware structure of these various processors is, more specifically, an electric circuit that combines circuit elements such as semiconductor elements.

[0137] The memory 98 stores instructions to be executed by the processor 96. The memory 98 includes a RAM (Random Access Memory) and a ROM (Read Only Memory), not shown. The processor 96 uses the RAM as a working area, executes software using various programs and parameters stored in the ROM, and executes various processes of the image forming apparatus 100 by using parameters stored in the ROM, etc.

[0138] <Other> The above-mentioned method for adjusting a liquid circulation device and the method for manufacturing an image forming device can be configured as a program for causing a computer to execute each process, and a non-temporary recording medium such as a CD-ROM (Compact Disk-Read Only Memory) storing this program can also be configured.

[0139] The technical scope of the present invention is not limited to the scope described in the above embodiments. The configurations and the like in each embodiment can be appropriately combined with each other without departing from the spirit of the present invention. [Explanation of symbols]

[0140] 1…Print media 10...Liquid circulation device 10K…Liquid circulation device 10C…Liquid circulation device 10M…Liquid circulation device 10Y…Liquid circulation device 10W…Liquid circulation device 12...Liquid tank 12A…Supply port 12B…Collection port 14…Supply side flow path 16…Recovery flow path 18I…Joint 18O…Joint 20...Joint 21…Head module 22…Degassing module 24…Supply side pump 26…Supply side filter 28…Supply side back pressure tank 28A…Liquid inlet 28B…Liquid outlet 28C…liquid chamber 28D…Air chamber 28E…Elastic membrane 30…Supply manifold 31...Supply side pressure sensor 32...Liquid supply channel 34...Liquid ejection head 36...Liquid recovery flow path 38...Bypass flow path 40…Print bar 40K…Print bar 40C…Print bar 40M…Print bar 40Y…Print bar 40W…Print bar 41A…Liquid supply port 41B…Liquid collection port 42...Bypass flow valve 60…Recovery manifold 62...Recovery side pressure sensor 64…Recovery back pressure tank 66…Recovery pump 68...Recovery filter 72...One-way valve 80…Flowmeter 90...Alarm device 95...Control device 96…Processor 98…Memory 100...Image forming apparatus 120...Transportation device 122…Pasrolla 130…Sending device 132…Feed roll 140...Pretreatment liquid application device 142... Application roller 144...Opposite roller 146...Pretreatment liquid drying device 150...Liquid application device 152...Printing drum 154…Scanner 170...Drying equipment 172...Drying drum 180... Winding device 182…Winding roll 200…Nozzle surface 202…Nozzle 204…Pressure chamber 208…Supply restriction 210…Supply tributary 212…Common flow path 214…Descender 216…Liquid circulation path 218…Recovery tributary 220...Common circulation flow path 228...Actuator 230…Nozzle plate 232...Flow path plate

Claims

1. a supply manifold that supplies liquid to a print bar that includes one or more liquid ejection heads that eject the liquid; a return manifold for returning the fluid from the printbar; a bypass flow path that communicates the supply manifold and the recovery manifold without passing through the print bar; Equipped with The liquid ejection head circulates the liquid due to a pressure difference between the supply manifold and the recovery manifold, The bypass flow path is capable of changing the resistance to the liquid. Liquid circulation device.

2. the print bar includes a plurality of the liquid ejection heads; The liquid ejection heads are arranged in one direction.

2. The liquid circulation system of claim 1.

3. where the maximum number of the liquid ejection heads that can be mounted on the print bar is an integer n, the resistance of the bypass flow path is 1 / n times or more and 1 time or less of the resistance of the liquid ejection head to the liquid.

2. The liquid circulation system of claim 1.

4. the resistance of the bypass flow path is changed according to the number of the liquid ejection heads; 2. The liquid circulation system of claim 1.

5. a pump that generates a pressure difference between the supply manifold and the recovery manifold; The resistance of the bypass flow path is changed according to the output value of the pump.

2. The liquid circulation system of claim 1.

6. a flow meter for measuring a flow rate of the liquid flowing into the supply manifold; The resistance of the bypass flow path is changed in response to the measured flow rate.

2. The liquid circulation system of claim 1.

7. a pump that generates a pressure difference between the supply manifold and the recovery manifold; The resistance of the bypass flow path is changed to a value that makes the output value of the pump within ±5% of a predetermined output value.

2. The liquid circulation system of claim 1.

8. a pump that generates a pressure difference between the supply manifold and the recovery manifold; a flow meter for measuring the amount of liquid flowing to the supply manifold and / or the return manifold; Equipped with The resistance of the bypass flow path is changed to a value that causes the flow rate of the liquid to be within ±5% of a predetermined flow rate.

2. The liquid circulation system of claim 1.

9. a notification device that notifies the user that a flow rate of the liquid flowing through the supply manifold has exceeded a predetermined threshold value; 9. A liquid circulation system according to claim 8.

10. the bypass flow path includes a bypass flow path valve; The resistance of the bypass flow path is changed by the bypass flow path valve. A liquid circulation device according to any one of claims 1 to 9.

11. a print bar having liquid ejection heads for ejecting liquid, the maximum number of liquid ejection heads that can be mounted on the print bar being an integer n; a supply manifold supplying the fluid to the printbar; a return manifold for returning the fluid from the printbar; a bypass flow path that communicates the supply manifold and the recovery manifold without passing through the print bar, the bypass flow path having a variable resistance to the liquid; a pump that generates a pressure difference between the supply manifold and the recovery manifold; A manufacturing method of an image forming apparatus comprising: m is an integer equal to or greater than 1 and less than n, m liquid ejection heads are mounted on the print bar; The resistance is set to 1 / (n-m) of the resistance of the liquid ejection head. A method for manufacturing an image forming apparatus.

12. a supply manifold that supplies liquid to a print bar having a liquid ejection head that ejects the liquid; a return manifold for returning the fluid from the printbar; a bypass flow path that communicates the supply manifold and the recovery manifold without passing through the print bar, the bypass flow path having a variable resistance to the liquid; a pump that generates a pressure difference between the supply manifold and the recovery manifold; A method for adjusting a liquid circulation device comprising: Closing the bypass flow path; Measure the output value of the pump; setting the resistance in response to the output value; A method for adjusting a liquid circulation device.

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